Add CloseRead and closeError test

example_test.go

@@ -74,11 +74,7 @@ func Example_writeOnly() {
 		ctx, cancel := context.WithTimeout(r.Context(), time.Minute*10)
 		defer cancel()
 
-		go func() {
-			defer cancel()
-			c.Reader(ctx)
-			c.Close(websocket.StatusPolicyViolation, "server doesn't accept data messages")
-		}()
+		ctx = c.CloseRead(ctx)
 
 		t := time.NewTicker(time.Second * 30)
 		defer t.Stop()

websocket.go

@@ -22,7 +22,7 @@ import (
 // and SetReadLimit.
 //
 // You must always read from the connection. Otherwise control
-// frames will not be handled. See the docs on Reader.
+// frames will not be handled. See the docs on Reader and CloseRead.
 //
 // Please be sure to call Close on the connection when you
 // are finished with it to release the associated resources.
@@ -319,10 +319,8 @@ func (c *Conn) handleControl(ctx context.Context, h header) error {
 // to be closed so you do not need to write your own error message.
 // This applies to the Read methods in the wsjson/wspb subpackages as well.
 //
-// You must read from the connection for close frames to be read.
-// If you do not expect any data messages from the peer, just call
-// Reader in a separate goroutine and close the connection with StatusPolicyViolation
-// when it returns. See the writeOnly example.
+// You must read from the connection for control frames to be handled.
+// If you do not expect any data messages from the peer, call CloseRead.
 //
 // Only one Reader may be open at a time.
 //
@@ -388,6 +386,21 @@ func (c *Conn) reader(ctx context.Context) (MessageType, io.Reader, error) {
 	return MessageType(h.opcode), r, nil
 }
 
+// CloseRead will close the connection if any data message is received from the peer.
+// Call this when you are done reading data messages from the connection but will still write
+// to it. Since CloseRead is still reading from the connection, it will respond to ping, pong
+// and close frames automatically. It will only close the connection on a data frame. The returned
+// context will be cancelled when the connection is closed.
+func (c *Conn) CloseRead(ctx context.Context) context.Context {
+	ctx, cancel := context.WithCancel(ctx)
+	go func() {
+		defer cancel()
+		c.Reader(ctx)
+		c.Close(StatusPolicyViolation, "unexpected data message")
+	}()
+	return ctx
+}
+
 // messageReader enables reading a data frame from the WebSocket connection.
 type messageReader struct {
 	c   *Conn

websocket_test.go

@@ -74,6 +74,50 @@ func TestHandshake(t *testing.T) {
 				return nil
 			},
 		},
+		{
+			name: "closeError",
+			server: func(w http.ResponseWriter, r *http.Request) error {
+				c, err := websocket.Accept(w, r, websocket.AcceptOptions{})
+				if err != nil {
+					return err
+				}
+				defer c.Close(websocket.StatusInternalError, "")
+
+				err = wsjson.Write(r.Context(), c, "hello")
+				if err != nil {
+					return err
+				}
+
+				return nil
+			},
+			client: func(ctx context.Context, u string) error {
+				c, _, err := websocket.Dial(ctx, u, websocket.DialOptions{
+					Subprotocols: []string{"meow"},
+				})
+				if err != nil {
+					return err
+				}
+				defer c.Close(websocket.StatusInternalError, "")
+
+				var m string
+				err = wsjson.Read(ctx, c, &m)
+				if err != nil {
+					return err
+				}
+
+				if m != "hello" {
+					return xerrors.Errorf("recieved unexpected msg but expected hello: %+v", m)
+				}
+
+				_, _, err = c.Reader(ctx)
+				var cerr websocket.CloseError
+				if !xerrors.As(err, &cerr) || cerr.Code != websocket.StatusInternalError {
+					return xerrors.Errorf("unexpected error: %+v", err)
+				}
+
+				return nil
+			},
+		},
 		{
 			name: "defaultSubprotocol",
 			server: func(w http.ResponseWriter, r *http.Request) error {